The role of refuges in biological invasions: A systematic review.

Aim: Ecological refuges buffer organisms against stressors and mediate a range of species interactions. However, their role in the context of biological invasions has yet to be synthesized, despite the increasing prevalence and impact of non‐native species. To address this, we conducted a systematic review aiming to determine the extent to which refuges are considered explicitly in the invasion literature and to synthesize their function. Location: Global. Time period: Present day. Major taxa studied: All. Methods: Our search of the literature was conducted using the SCOPUS and Web of Science databases and followed the preferred reporting items for systematic reviews and meta‐analyses (PRISMA) protocol. We obtained 315 records of refuge use in biological invasions from 300 studies. From each record, we extracted information relating to the experimental design, species characteristics and refuge type, where available. Results: Refuges and refuge‐mediated processes are widely reported in the invasion literature. Native species commonly use refuges to avoid non‐native predation and competition, with spatial complexity and habitat heterogeneity key factors in facilitating their coexistence. Records show that artificial structures safeguard non‐natives in their introduced range. However, there were key differences in the use of such structures in marine and terrestrial environments. Moreover, the enhanced structural complexity created by non‐native plants and bivalves is often reported to act as a predation refuge for other species. Main conclusions: The ubiquity of refuge‐based processes suggests that refuges can play an important role in affecting the persistence, spread and impacts of non‐native species, either through previously described mechanisms (i.e. refuge‐mediated apparent competition and the persistent pressure scenario) or through a mechanism we describe (i.e. when non‐native species use existing refuges), or both. [ABSTRACT FROM AUTHOR]